Apparatus for recycling alkane immersion liquids and methods of employment

Abstract

The present invention provides a clean closed loop fluid transport system and methods for recycling low absorbance liquid alkanes. The alkanes can be advantageously employed as immersion liquids in the production of electronic or integrated optical circuit elements by photolithographic methods employing ultraviolet wavelengths.

1 . An apparatus comprising: a clean closed loop fluid transport system comprising an adsorbent segment; a filtration segment; a photo-imaging segment having a point of entry; tubes disposed to connect said segments; a pump disposed to cause a fluid to flow through said tubes to and from said segments; a means for delivering and removing a fluid to and from said photo-imaging segment; and a liquid alkane contained within the apparatus, wherein at the point of entry of the photo-imaging segment thereof said liquid alkane has an absorbance at 193 nm of less than 0.40 cm −1 .  
   
   
       2 . The apparatus of  claim 1  further comprising a deoxygenating segment.  
   
   
       3 . The apparatus of  claim 1  further comprising a degassing segment.  
   
   
       4 . The apparatus of  claim 1  wherein said filtration segment lies downstream from said adsorbent segment.  
   
   
       5 . The apparatus of  claim 1  further comprising an in-line ultraviolet spectrophotometer.  
   
   
       6 . The apparatus of  claim 1  wherein the liquid alkane is selected from the group consisting of cyclopentane, cyclohexane, cycloheptane, cyclooctane, decane, decahydronaphthalene racemate, cis-decahydronaphthalene, trans-decahydronaphthalene racemate, exo-tetrahydrodicyclopentadiene, 1,1′-bicyclohexyl, 2-ethylnorbornane, n-octyl-cyclohexane, dodecane, tetradecane, hexadecane, 2-methyl-pentane, 3-methyl pentane, 2,2-dimethyl butane, 2,3-dimethyl butane, octahydroindene, and mixtures thereof.  
   
   
       7 . The apparatus of  claim 6  wherein the liquid alkane is selected from the group consisting of 2-methylpentane, 3-methylpentane, 2,3-dimethylbutane, 2,2-dimethylbutane, decane, dodecane, tetradecane, hexadecane, cyclohexane, cycloheptane, cyclooctane, 2-ethylnorbornane, octahydroindane, bicyclohexyl, decahydronaphthalene, exo-tetrahydrodicyclopentadiene, and mixtures thereof.  
   
   
       8 . The apparatus of  claim 7  wherein the liquid alkane is selected from the group consisting of bicyclohexyl, decahydronapthalene, exo-tetrahydrodicyclopentadiene, and mixtures thereof.  
   
   
       9 . The apparatus of  claim 1  wherein the absorbance at 193 nm of said liquid alkane is <0.22 cm −1 .  
   
   
       10 . The apparatus of  claim 1  wherein the absorbance at 193 nm of said liquid alkane is <0.15 cm −1 .  
   
   
       11 . The apparatus of  claim 1  wherein the adsorbent is selected from the group consisting of 3A molecular sieves, 4A molecular sieves, 5A molecular sieves, 13X molecular sieves, silica, neutral alumina, basic alumina, acidic alumina, activated carbon, and combinations thereof.  
   
   
       12 . The apparatus of  claim 11  wherein the adsorbent is activated.  
   
   
       13 . The apparatus of  claim 1  wherein the adsorbent segment is a chromatographic column.  
   
   
       14 . The apparatus of  claim 2  wherein the deoxygenation segment is a membrane degasser.  
   
   
       15 . The apparatus of  claim 1  wherein the photo-imaging segment is a photolithographic system.  
   
   
       16 . The apparatus of  claim 15  wherein the photolithographic system comprises an optical illumination system comprising an optical element, a photoresistive surface disposed to be imagewise illuminated by said optical illumination system, a gap between the optical element and the photoresistive surface, and said liquid alkane disposed to fill the gap between the optical element and said photoresistive surface.  
   
   
       17 . The apparatus of  claim 16  wherein the optical illumination system comprises a 193 nm light source.  
   
   
       18 . The apparatus of  claim 16  wherein the optical illumination system comprises a plurality of optical elements.  
   
   
       19 . The apparatus of  claim 1  wherein the photo-imaging segment comprises an optical stepper.  
   
   
       20 . A method for performing liquid immersion photolithography comprising: 
 providing a clean closed loop fluid transport system comprising an adsorbent segment, a filtration segment, a photo-imaging segment, tubes disposed to connect said segments, a pump disposed to cause a fluid to flow within the system, a means for delivering and removing a fluid to and from said photo-imaging segment; and a means for purging absorbed gas from a fluid;    causing a liquid alkane having an absorbance at 193 nm of <0.40 cm −1  to be introduced into the photo-imaging segment;    disposing the liquid alkane between a light source and a surface undergoing imagewise illumination by the light source;    causing the liquid alkane to flow from the photo-imaging segment to the adsorbent segment through the tubes;    optionally deoxygenating the liquid alkane by purging absorbed oxygen from the liquid alkane;    contacting the liquid alkane with an adsorbent, the contacted liquid alkane after said contacting having an absorbance at 193 nm of <0.40 cm −1 ;    and causing the contacted liquid alkane to flow from the adsorbent segment to said photo-imaging segment.    
   
   
       21 . The method of  claim 20  wherein said means for purging absorbed gas comprises a membrane degasser.  
   
   
       22 . The method of  claim 20  wherein said deoxygenating comprises sparging said alkane with an inert gas.  
   
   
       23 . The method of  claim 20  wherein said filtration segment lies downstream from said adsorbent segment.  
   
   
       24 . The method  claim 20  wherein said fluid transport system further comprises an in-line ultraviolet spectrophotometer.  
   
   
       25 . The method of  claim 20  wherein in said fluid transport system the liquid alkane is selected from the group consisting of cyclopentane, cyclohexane, cycloheptane, cyclooctane, decane, decahydronaphthalene racemate, cis-decahydronaphthalene, trans-decahydronaphthalene racemate, exo-tetrahydrodicyclopentadiene, 1,1′-bicyclohexyl, 2-ethylnorbornane, n-octyl-cyclohexane, dodecane, tetradecane, hexadecane, 2-methyl-pentane, 3-methyl pentane, 2,2-dimethyl butane, 2,3-dimethyl butane, octahydroindene, and mixtures thereof.  
   
   
       26 . The method of  claim 25  wherein in said fluid transport system the liquid alkane is selected from the group consisting of 2-methylpentane, 3-methylpentane, 2,3-dimethylbutane, 2,2-dimethylbutane, decane, dodecane, tetradecane, hexadecane, cyclohexane, cycloheptane, cyclooctane, 2-ethylnorbornane, octahydroindane, bicyclohexyl, decahydronaphthalene, exo-tetrahydrodicyclopentadiene, and mixtures thereof.  
   
   
       27 . The method of  claim 26  wherein in said fluid transport system the liquid alkane is selected from the group consisting of bicyclohexyl, decahydronapthalene, exo-tetrahydrodicyclopentadiene, and mixtures thereof.  
   
   
       28 . The method of  claim 20  wherein the absorbance at 193 nm of said liquid alkane is <0.22 cm −1 .  
   
   
       29 . The method of  claim 20  wherein the absorbance at 193 nm of said liquid alkane is <0.15 cm −1 .  
   
   
       30 . The method of  claim 20  wherein in said fluid transport system the adsorbent is selected from the group consisting of 3A molecular sieves, 4A molecular sieves, 5A molecular sieves, 13X molecular sieves, silica, neutral alumina, basic alumina, acidic alumina, activated carbon, and combinations thereof.  
   
   
       31 . The method of  claim 20  wherein in said fluid transport system the adsorbent is activated.  
   
   
       32 . The method of  claim 20  wherein in said fluid transport system the adsorbent segment is in the form of a chromatographic column.  
   
   
       33 . The method of  claim 21  wherein in said fluid transport system the deoxygenation segment is in the form of a membrane degasser.  
   
   
       34 . The method of  claim 20  wherein in said fluid transport system the photo-imaging segment is a photolithographic system for fabricating integrated electronic and optical circuit elements.  
   
   
       35 . The method of  claim 34  wherein in said fluid transport system the photolithographic system comprises an optical illumination system comprising an optical element, a photoresistive surface disposed to be imagewise illuminated by said optical illumination system, a gap between the said optical element and said photoresistive surface, and said liquid alkane is disposed to fill the gap between the said optical element and said photoresistive surface.  
   
   
       36 . The method of  claim 35  wherein in said fluid transport system the optical illumination system further comprises a 193 nm light source.  
   
   
       37 . The method of  claim 35  wherein in said fluid transport system the optical illumination system further comprises a plurality of optical elements.  
   
   
       38 . The method of  claim 20  wherein the photo-imaging segment comprises an optical stepper.  
   
   
       39 . A method for cleaning a metal surface, comprising contacting the metal surface with elemental fluorine gas for a period of 1 to 48 hours, such that later contact of an immersion liquid with the cleaned metal surface increases the A/cm of said liquid by less than 0.02 cm −1 .  
   
   
       40 . The method of  claim 39  wherein the metal is stainless steel.  
   
   
       41 . The method of  claim 39  wherein the fluorine gas is used as 1 to 50% F 2  in nitrogen.  
   
   
       42 . The method of  claim 39  wherein the contacting is carried out for about 12 hours.  
   
   
       43 . The method of  claim 39  wherein the fluorine gas is used as 25% F 2  in nitrogen.  
   
   
       44 . A method of cleaning a metal surface, consisting of heating the metal surface, to 350-500° C., in air for a period of 4 to 24 hours, such that later contact of an immersion liquid with that surface increases the A/cm of said fluid by <0.02 cm −1 ,  
   
   
       45 . The method of  claim 39  wherein the metal is stainless steel.